Cynthia Curl

Project title: Characterizing Dietary Exposure to Organophosphate Pesticides, Incorporating Organic Food Consumption, for Use in Epidemiological Research

Degree: PhD | Program: Environmental and Occupational Hygiene (EOHY) | Project type: Thesis/Dissertation
Completed in: 2014 | Faculty advisor: Joel D. Kaufman


Concern exists about the potential for low-level exposure to organophosphate pesticides (OPs) to lead to neurological and cognitive health effects. OPs are the most widely used insecticides in American agricultural, and diet is thought to be the primary route by which the general public is exposed to OPs. The United States Department of Agriculture permits food to be certified “organic” when grown according to specific regulations, including prohibitions on the use of most synthetic pesticides. While organic food consumption is known to reduce exposure to OPs, health benefits from choosing organic food have not been demonstrated. We aimed to develop a novel method to assess long-term dietary OP exposure, designed to avoid many of the limitations of the existing methods of OP exposure assessment. Using a combination of individual-level information on dietary intake and national-level data on pesticide residue levels on food items, we estimated long-term dietary OP exposure in a multi-city, multi-ethnic population of over 4,000 adults. We assessed the face validity of this method by evaluating its comparability with urinary biomonitoring in a subset of participants. Among individuals with conventional diets, increasing tertile of estimated dietary OP exposure was associated with higher urinary metabolite concentrations. We also found that metabolite concentrations were significantly lower in people reporting more frequent consumption of organic produce. We further aimed to better understand the individual- and neighborhood-level characteristics associated with organic food consumption. We observed that women, younger individuals and those with higher education were more likely to consume organic food, and that neighborhood produce availability was also associated with organic food consumption. Our third and final aim was to evaluate the association between the long-term dietary OP exposure we developed and cognitive outcomes, accounting for the individual- and neighborhood-level variables that were associated with organic food consumption. We observed a relationship between increasing dietary OP exposure and decrements in the phonological loop component of working memory as assessed by the Forward Digit Span Test, but did not find OP exposure to be associated with three other cognitive endpoints. The results of this study suggest that the new method we have developed to assess dietary pesticide exposure will be useful in future epidemiological studies of the health effects of low-level exposure to OPs.